The present invention relates to a device for analyzing the composition of a substance, and more particularly to an ion-emission microanalyzer microscope intended for investigation of metal alloys and other solid materials by observing the surface structure of an object under investigation and by local and in-depth chemical and isotopic analysis.
Ion microanalyzers are known in which an object under investigation is bombarded with ions focused to a narrow beam (microprobe), and the secondary ions knocked out from the object are analyzed by means of a mass filter. In such microanalyzers, the problem of controlled selection of a portion of the object under investigation for mass-spectrometric analysis is solved by using mirror-lens optical microscopes, some of whose optical elements are in direct proximity to the object, whereby they can be contaminated with dust particles in the course of analysis, the performance of the microanalyzer.
Moreover, in the case of microprobes, difficulties arise in locating the point of bombardment in the course of analysis because the perceptible crater is formed only after the analysis is over. Local in-depth analysis is rendered difficult by the effect of the crater walls, particularly when the probe diameter is small.
Also known are microanalyzer microscopes in which the ionic image of the surface of an object under investigation, formed by the secondary ions knocked out from the object's surface by the ion beam is separated into elemental images in a magnetic mass filter. A separated image element formed by ions of a particular type is displayed on a luminescent screen with the aid of an ion-optical converter. In this case, the image is representative of the distribution topography only for that particular chemical element. Analysis of different chemical elements on the object's surface areas whose dimensions are determined by the optical resolution of the instrument, is made difficult in such a device because, as a result of the ion-optical converter being located behind the magnetic mass filter, the image of the object on the luminescent screen is shifted each time the mass filter is readjusted from one mass to another.
There is also known an ion-emission microanalyzer microscope comprising a vacuum chamber accommodating an ion source with a focusing system for bombarding the surface of an object under investigation, and the following components arranged in series along the beam of secondary ions emitted by the bombarded object's surface: an immersion objective, an aperture diaphragm, an aperture for separating an image element, a mass filter, and an ion detector. In addition, this prior art microanalyzer microscope includes a recording device located outside the vacuum chamber and connected to the output of the ion detector.
Such a microanalyzer microscope permits analysis of an object, with its spatial resolution being determined by the optical resolution of the microscope; however, no provision is made for selecting and locating the point at which local analysis is to be performed during analysis itself, and additional means for specifying the point of local analysis are required.
The principal object of the invention is to provide an ion-emission microanalyzer microscope in which the point of local analysis can be determined during analysis itself.
Another object of the invention is to provide an ion-emission microanalyzer microscope permitting selection of the point of local analysis.
Still another object of the invention is to provide an ion-emission microanalyzer microscope permitting local analysis of an object's surface over an area smaller than that impinged upon by the primary ion beam.
Yet another object of the invention is to provide an ion-emission microanalyzer microscope permitting the spatial resolution of analysis to be altered without changing the size of the primary beam incident upon the object.